Fefnir, known as Fafnir in some translations, is one of the Four Guardians in the Rockman Zero (Mega Man Zero) series. He serves as the guardian of the Reploid army and specializes in fire-based attacks and heavy artillery. Fefnir is characterized by his warrior spirit, love for battle, and sense of honor. Despite being an antagonist, he respects his opponents, especially Zero, and often seeks to test his strength in combat. His loyalty to Neo Arcadia and Harpuia is unwavering.